CETR OVERALL ABSTRACT Widespread antimicrobial resistance (AMR), both in the USA and globally, has made it increasingly difficult to treat enteric and invasive nosocomial bacterial infections that were previously responsive to antimicrobials. Among the most important enteric bacterial pathogens that cause severe clinical disease and death if they cannot be treated with effective antibiotics are ones that cause diarrhea, dysentery or enteric fever. Some bacterial enteric pathogens are epidemiologically emerging or re-emerging, e.g.: multi-drug resistant H58 lineage of Salmonella Typhi; S. Paratyphi A; multi-drug resistant Shigella; drug-resistant Campylobacter jejuni and Clostridium difficile. A few bacterial enteropathogens are of special interest from the civilian biodefense perspective, as they have been used by nefarious individuals to promulgate bioterror (non-typhoidal Salmonella [NTS]), or have properties that suit them to such a purpose (Shigella dysenteriae 1). Two of the most important opportunistic drug-resistant bacterial pathogens that cause invasive infections in compromised hosts are Klebsiella pneumoniae and Pseudomonas aeruginosa. Vaccines and other preventives against these pathogens can ameliorate the AMR problem by preventing clinical disease, thereby precluding the need to administer antibiotics and relieving selection pressure. The five projects described in this Center of Excellence for Translational Research (CETR) proposal, bonded by the theme ?Active Vaccination and Passive Antibody Strategies to Prevent Disease Caused by Multidrug-Resistant Bacterial Pathogens?, will undertake translational research towards developing the following countermeasures to prevent disease caused by important multi-drug resistant bacterial pathogens: an improved Shigella live vector vaccine consisting of 6 attenuated strains of key serotypes, each expressing protective antigens to prevent clinical illness caused by ETEC, as well as Shigella (Project 1); engineered attenuated NTS strains representing serogroups B, C1, C2 & D to serve as a multivalent broadly protective live oral vaccine (Project 2); a conjugate vaccine consisting of O polysaccharides of K. pneumoniae serotypes O1, O2, O3 & O5, representing the vast majority of invasive isolates, linked to flagellin type A or B of P. aeruginosa, to prevent invasive disease (Project 3); the probiotic yeast Saccharomyces boulardii engineered to secrete antibodies against K. pneumoniae fimbriae that mediate intestinal colonization, thereby diminishing a major risk factor (colonization) for invasive disease (Project 3); recombinant S. boulardii that secrete antibodies directed against C. difficile toxins and somatic antigens or against flagellin of C. jejuni, administered orally to inhibit gut colonization and prevent diarrheal disease (Project 4); a compendium of immune response measurements to Salmonella serovars to identify correlates of protection and guide development of broadly protective live oral Salmonella vaccines (Project 5). Translational research will advance these countermeasures to where Investigational New Drug Applications (IND) can be prepared to initiate Phase 1 clinical trials.